Investigate the effect of the mass of a copper anode in the electrolyte of Copper Sulphate solution.

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Introduction

Adam Pattenden 10S Investigate the effect of the mass of a copper anode in the electrolyte of Copper Sulphate solution Plan In this investigation I will be trying to find out the change in mass of a copper anode during electrolysis. I will be changing certain factors to see how these affect the mass of a copper anode. Some of the factors that will affect the mass of a copper anode are: 1) Time- If this was used as a variable/factor then I predict that the longer the time, the greater the decrease in mass of the copper anode. 2) Current- if this was used then I predict that the greater the current is, the greater the decrease in mass will be. 3) Voltage- if this was used then I predict that the greater amount of voltage would mean a greater decrease in mass of the copper anode. ...read more.

Middle

Apparatus Measuring cylinder 250 ml beaker beaker 75 ml of copper sulphate (concentration= 0.25 M) Power pack Electrodes (anode = copper, cathode = zinc) Stopwatch Scales Wires Crocodile clips Propanone Diagram Method 1) I will weigh the copper anode and record its mass 2) I will then set up the apparatus as shown in diagram 3) I will turn the voltage on the power pack up to 9 4) After 2 minutes I will take out the anode and dip it in Propanone. This evaporates any of the copper sulphate on the copper so that it does not affect the mass. Then I will weigh the anode and record the results. 5) I will repeat these steps and weigh the anode after every 2 minutes up to 20 minutes and record the results. Results Time (m) Loss of mass of the anode (g) 0 0 2 0.01 4 0.01 6 0.02 8 0.03 10 0.04 12 0.05 14 0.06 16 0.07 18 0.08 20 0.09 Conclusion The results have told me that as time increases the mass of the copper anode decreases. ...read more.

Conclusion

I thought that we did take a sufficient amount of results us maybe a few more would have given us a clearer graph and a slightly better conclusion. Our range of results was good because we did from 0 minutes to 20 minutes taking a sample every 2 minutes. We could not have taken results from over 20 minutes because we did not have enough time. We did get an anomalous result; this was taken at 2 minutes. It was anomalous because the scales that we used to weigh the anode were inaccurate so I used different scales for the rest of the experiment. If I were to do this experiment again I would have repeated the whole experiment with a different anode and cathode to see if the graph was the same and that the results were similar. This would have given me harder evidence to write my conclusion with. Other factors I would like to have investigated were the concentration of the copper sulphate and also the volume of the copper sulphate. ...read more.

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As there would no longer be any movement of the molecules, no energy would be transferred. This is unlikely to be a cause of the drop in the current generated at 0.9 and 1 concentrates however, as not enough time was given.

the cathode are smaller than they should be and at the anode they are larger than they should be. Strangely the worst results, those which are furthest from the average aren't those at the highest currents but the anode reading 0.85A and the cathode readings at 0.6A and 0.35A.

This may suggest that the results were not very accurate. Although both of these results, 0.0315g gained and 0.032g lost were very close, they both lay on very different places on each of the lines drawn. This suggests either error on those two results, or for the rest of them.

Both electrodes are immersed to a depth of 3cm in 1.0 mole dm Copper sulphate solution The Variable resistor is adjusted to give the desired current which could be read by looking at the ammeter. The variable resistor maintains a low and steady current.

0.08 0.1 0.12 These masses should be the same as the mass lost at the anode. I have drawn a graph showing these results; it supports the prediction of direct proportion, as it is a straight line that goes through the origin.

Also, before weighing the anode and cathode, I shall place them gently onto a paper towel, to remove some excess water, whilst being very careful not to remove any copper from the cathode. This should unfortunately be the most inaccurate part of the experiment.

Cu Cu2+ - 2e- As a result of this, the anode is worn away as the copper is decomposed, and oxygen is formed, while at the cathode mass is gained because copper is formed on it and creates plating. When the copper anode decomposes it loses 2 electrons and copper ions, which have a positive charge.